android 4.2获取不到手机信号强度

Question

4.2获取信号强度的监听没有改啊.为什么现在每次获取都是0啊.public class MainActivity extends Activity { private TelephonyManager Tel;
private MyPhoneStateListener MyListener; @Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main); MyListener = new MyPhoneStateListener();
Tel = (TelephonyManager) getSystemService(Context.TELEPHONY_SERVICE); Tel.listen(MyListener, PhoneStateListener.LISTEN_SIGNAL_STRENGTHS);
} private class MyPhoneStateListener extends PhoneStateListener { @Override
public void onSignalStrengthsChanged(SignalStrength signalStrength) { super.onSignalStrengthsChanged(signalStrength); Toast.makeText(getApplicationContext(),"Go to Firstdroid!!! GSM Cinr = "+ String.valueOf(signalStrength.getGsmSignalStrength()),
Toast.LENGTH_SHORT).show(); } }; @Override
protected void onPause() { super.onPause(); Tel.listen(MyListener, PhoneStateListener.LISTEN_NONE); } /* Called when the application resumes */ @Override
protected void onResume() { super.onResume(); Tel.listen(MyListener, PhoneStateListener.LISTEN_SIGNAL_STRENGTHS); }}android信号强度